Composite pyrotechnic product with non-crosslinked binder and method for preparing same

ABSTRACT

A composite pyrotechnic product, especially a propellant powder for barrel weapons, has a composition, expressed as weight percentages, that contains from 78% to 90% of organic energetic charges, and from 10% to 22% of a polymeric gum, chosen from polyurethane-polyester gums, polyurethane-polyether gums and mixtures thereof, the number-average molecular weight of which is greater than 20 000 g/mol and the Mooney viscosity of which is between 20 and 70 ML (5+4) at 100° C.

The present invention relates to composite pyrotechnic products, whichare suitable especially as propellant powders for barrel weapons (moreparticularly for tank artillery). It concerns composite pyrotechnicproducts, containing a high content of energetic charges in a binder.Said products are particularly advantageous, especially in terms offorce (of energetic power), of vulnerability (see below a reminderregarding this notion, which is familiar to those skilled in the art),and of field of application as regards the nature of the charges theymay contain. They may conveniently be optimized in terms of erosivity.

A subject of the present invention is also a process for preparing saidcomposite pyrotechnic products. Said process is particularly easy toperform.

“Homogeneous” propellant powders constituted by one or more gelatinizedenergetic bases having a homogeneous appearance (whence their name) areknown. Among the most widely known homogeneous propellant powders,mention may be made of “smokeless” powders based on nitrocellulose aloneor based on a nitrocellulose-nitroglycerine mixture. In order to improvethe energy performance of these “homogeneous” powders, it is sought toincorporate therein organic (pulverulent) energetic charges. Thesecharged powders no longer have a homogeneous appearance, but aheterogeneous appearance in which are distinguished, on the one hand,the energetic binder, and, on the other hand, the charges. Such chargedpowders are referred to as “composite” or “heterogeneous” powders. Suchcharged powders are described, for example, in French patent applicationFR 2 488 246.

Use of the energetic binder nitrocellulose however has the drawback ofmaking these powders vulnerable. The term “vulnerability” refers to theproperty that the powders have of being able to ignite and deflagrateunder the, effect of an undesired, random physical phenomenon, forinstance the impact of a projectile. Vulnerability is a major defect forpowders intended to be transported on combat tanks. The development ofmodern combat machines thus led those skilled in the art to seeksparingly vulnerable propellant powders.

With this in mind, composite powders with an inert binder were proposed(constituted mainly of organic energetic charges in a synthetic resin).Such powders are markedly less vulnerable than homogeneous or compositepowders with an energetic binder (nitrocellulose). However, since theycontain an inert binder, these powders must, in order to deliver thenecessary energy during their ignition, contain very high levels ofcharges, often in the region of 80% of the total weight of the powder.Composite powders with an inert binder thus have the characteristic ofcontaining very little binder relative to their pulverulent charge. Theprecursor mixtures of these powders must, however, be able to be worked(in particular be able to be calendered or drawn through a die ofrelatively small diameter, usually comprising pins intended to createchannels present in the final powder strand), and the powders mustconserve their geometrical shape over time. It is particularly inreference to the production of these composite propellant powders withan inert binder for barrel weapons that those skilled in the art came upagainst and are still coming up against serious difficulties.

The inert binders, of synthetic origin, that may be used in thepreparation of composite pyrotechnic products and that are present intheir composition exist to date as thermoplastic binders and asthermosetting binders (thermosetting binders obtained from oligomers).

Those skilled in the art first turned toward the use of thermoplasticinert binders. Specifically, such thermoplastic binders allow, intheory, while raising temperature, mechanical working of the product togive it the desired geometry. Obviously, however, the workingtemperature (at which the binder is deformable) should be compatiblewith the stability of the charges present and, in reference to thisunavoidable requirement, it is often necessary to use a solvent. The useof such a solvent complicates the implementation of the process. Patentapplication EP 0 036 481 describes a process for manufacturing compositeexplosives with a thermoplastic binder. Patent application IN498/DEL/2001 describes a process for preparing propergol containinghexogen charges (RDX) in a thermoplastic binder. Composite products witha thermoplastic binder are generally not entirely satisfactory, sincetheir mechanical properties are too sensitive to thermal variations.

Those skilled in the art then turned toward the use of thermosettinginert binders (obtained from oligomers), such as (crosslinkable)polyurethane binders, making it possible, after crosslinking, toconstitute a three-dimensional network (in which the charges are foundcoated), i.e. to definitively set the geometry of the powder grain(finally obtained). The industrial scale manufacture of powders (ingeneral composite pyrotechnic products) with a crosslinked inert binder(thus essentially constituted of a high content of charges in a minimumamount of binder) remains very difficult firstly due to the minimumcohesion and mechanical strength required for the product beforecrosslinking (in order to form it) and secondly due to the limited “potlife” of thermosetting resins (the term “pot life” means the period ofcommencement of crosslinking of the resin during which it may be workedlike a plastic). Furthermore, obviously, the crosslinking temperaturemust be compatible with the stability of the charges and thecrosslinking agent used must itself also be compatible with saidcharges.

Confronted with these difficulties, in the context of usingthermosetting binders:

-   -   those skilled in the art proposed to work in the presence of        solvents. A solvent-based process was especially described in        French patent application FR 2 268 770. Such processes are,        however, difficult and expensive to implement, and        unsatisfactory at the industrial scale;    -   to work without solvent, with thermosetting binders, said        persons skilled in the art have widely resorted to the “casting”        or “global” technique, which consists in simultaneously mixing        in a blender the liquid elementary constituents of the resin and        the energetic charges and in casting, before polymerization, the        mixture thus obtained in a mold in order to perform the actual        polymerization therein. This technique, which has been widely        described, for example in French patent applications FR 2 109        102, FR 2 196 998, FR 2 478 623 and FR 2 491 455, may be        suitable for manufacturing composite solid propergols for rocket        or missile engines, or alternatively for manufacturing composite        explosives for device heads, which are usually used in the form        of wide-diameter products, but proves to be entirely unsuitable        for the industrial manufacture of large, medium and small        caliber composite powders and more generally for that of certain        composite pyrotechnic products;    -   for the solvent-free manufacture of composite pyrotechnic        products with a thermosetting inert binder, especially of small        diameters, said persons skilled in the art have available, at        the present time, only the following two techniques:        -   a) the first which consists in mixing in a blender the            constituents of the. resin with the energetic charges, in            initiating crosslinking of the resin and, during            crosslinking, in forming the product, within a very short            space of time, as described, for example, in French patent            applications FR 1 409 203 and FR 2 159 826. This technique            requires precise control of the crosslinking kinetics in            order to be able to work the paste and, as a result, it is            difficult to manage at the industrial scale;        -   b) the second, which is much more efficient, including at            the industrial scale, described in patent application EP 0            194 180. The composite pyrotechnic products obtained via            this second technique are constituted mainly, on the one            hand, by a polymeric binder (for example polyurethane)            obtained by reaction of a polyhydroxylated prepolymer            (polymer) (with a number-average molecular weight of between            2000 and 5000 and a mean functionality of hydroxyl groups            (OH greater than 2 and less than 3) (PBHT, polyether or            polyester, for example) with a crosslinking agent            (diisocyanate), and, on the other hand, by an energetic            charge, preferentially of octogen (HMX) or of hexogen (RDX),            in a content of about 80% by weight. Said second technique            consists:            -   in a first step, in mixing said polyhydroxylated                prepolymer with said energetic charge and with an amount                of diisocyanate of between 50% and 90% by weight of the                stoichiometric amount required for total polymerization                (reaction) of all the hydroxyl groups (OH) of said                prepolymer and in performing the condensation reaction                of the isocyanate groups (NCO) on the hydroxyl groups                (OH) so as to obtain a partially polymerized                (crosslinked) paste;            -   in a second step, in mixing with said partially                polymerized (crosslinked) paste thus obtained the                remainder of the diisocyanate required to achieve said                stoichiometric amount required for total polymerization                (crosslinking) and in extruding the pasty mixture thus                obtained; and then            -   in a third step, in completing, by hot curing, the                condensation reaction of the isocyanate groups (NCO)                added during the second step to the hydroxyl groups (OH)                that are still free.

The technique under consideration thus comprises two polymerization orcrosslinking steps, more precisely a first step of pre-crosslinking (orfirst crosslinking phase) with an amount of isocyanate that allows theproduction of a partially polymerized (crosslinked) paste, havingmechanical strength and cohesion suitable for the implementation of therest of the process (especially extrusion) and a second step ofcrosslinking leading to the final product with the desired crosslinkedbinder. In this, said technique overcomes the two types of difficultymentioned above (difficulty due to the lack of mechanical strength andcohesion of the product to be extruded and problem of the “pot life”).

With reference to this second technique, it should, however, be notedthat the operations for metering out the crosslinking agent(diisocyanate) to perform the pre-crosslinking are difficult. Theyrequire great precision. Moreover, the field of application of saidtechnique is limited, in view of the nature of the crosslinking agentinvolved (of isocyanate type, to react with hydroxyl functions), asregards the nature of the energetic charges present, insofar as certainenergetic charges (having intrinsic acidity) are capable of reacting, ina spurious reaction, with said crosslinking agent (of isocyanate type)present. The presence of such charges (EDNA, nitropyrazoles, forexample) thus poses a problem for managing the complementarypre-crosslinking and crosslinking steps. Now, this presence is far fromtrivial, in the context of the present invention, that of compositepyrotechnic products, especially propellant powders for barrel weapons.Specifically, in this context, the use of high contents of energeticcharges (see above), especially high contents of charges of RDX type, istargeted. Now, a person skilled in the art knows the negative impact ofa high content of such charges on the erosivity of the powder containingit. Replacing at least part of the RDX with other energetic charges(such as EDNA), which are less erosive, is thus desirable. It wouldtherefore be highly advantageous to have available a novel type ofbinder, which removes the need to use isocyanate crosslinking agents.

In such a context, the inventors propose composite pyrotechnic productsthat are especially suitable as propellant powders for barrel weapons,of novel type. These (novel) composite pyrotechnic products contain ahigh content of charges in a binder of a novel type (this binder isneither a thermoplastic binder, nor a thermoset (thermocrosslinked)binder). Said (novel) composite pyrotechnic products are particularlyvaluable in terms of force (they contain a high content of energeticcharges), of vulnerability (they do not contain any nitrocellulose andmay advantageously contain sparingly vulnerable energetic charges) andof production process (their production process is particularly easy toperform (in particular, it comprises no crosslinking step and thereforedoes not involve the use of crosslinking agent(s)) and they may also beoptimized in terms of erosivity (they may advantageously contain EDNAcharges in total or partial replacement for RDX charges). They are infact liable to contain any type of organic energetic charge (see thebroad field of application of the products of the invention as regardsthe nature of the charges mentioned above) insofar as, in the absence ofcrosslinking agent, no spurious reactions need to be feared(charges/crosslinking agent(s)).

According to its first subject, the present invention thus relates tonovel composite pyrotechnic products. Characteristically, theircompositions, expressed as weight percentages, contain:

-   -   from 78% to 90%, advantageously from 80% to 86%, of organic        energetic charges, and    -   from 10% to 22% of a polymeric gum, chosen from        polyurethane-polyester gums, polyurethane-polyether gums and        mixtures thereof, the number-average molecular weight of which        is greater than 20 000 g/mol and the Mooney viscosity of which        is between 20 and 70 ML (5+4) at 100° C.

As indicated above, the composite pyrotechnic products of the inventionthus contain a high content of organic energetic charges in a binder ofa novel type: a binder, of non-crosslinked gum (“raw rubber”) type. Itis seen later that said binder may contain a plasticizer.

The composite pyrotechnic products of the invention thus contain a highcontent of organic energetic charges: from 78% to 90% by weight,advantageously from 80% to 86% by weight.

The charges under consideration (organic charges of any type (notselected, as in the context of thermocrosslinkable binders, taking intoaccount the crosslinking reaction to ultimately by implemented); mineralcharges having been set aside insofar as they generate solid particles)are not per se original. They are organic energetic charges that areknown per se and, for the most part, are already conditioned accordingto the prior art in a conventional organic polymeric binder (such asPBHT), especially crosslinked. The charges are advantageously hexogen(RDX), octogen (HMX), nitroguanidine (NGU), ethylene dinitramine (EDNA),N-guanylurea dinitramide (FOX 12 (GUDN)),1,1-diamino-2,2-dinitroethylene (FOX 7 (DADE)), bis(triaminoguanidinium)5,5′-azotetrazolate (TAGZT), dihydrazinium 5,5′-azotetrazolate (DHDZT),5,5′-bis(tetrazolyl)hydrazine (HBT), bis(2,2-dinitropropyl)nitramine(BDNPN), a nitropyrazole, or a mixture of these energetic charges.

Within the composite pyrotechnic products of the invention there is thusa type of energetic charges, advantageously chosen from the above list,or a mixture of at least two types of energetic charges, advantageouslychosen from the above list. EDNA organic energetic charges arepreferably found therein. A mixture of EDNA charges and of RDX chargesis particularly preferably found therein. It is in no way excluded tofind only RDX charges or only EDNA charges, but, as indicated above,mixtures of EDNA charges and of RDX charges make it possible to achievean optimum with reference to the force/erosivity compromise. It has beenunderstood that the more said mixtures contain RDX, the more energeticthey are, but the more erosive they are.

Energetic charges are in the form of solid grains homogeneouslydistributed in the binder. These solid grains advantageously have, in amanner known per se, several particle size distributions.

The organic energetic charges are thus present in a novel binder. Saidnovel binder is based on a gum of the type mentioned. According to onevariant, it consists essentially of said gum (at least one additivebeing present in small amount), or even it consists of said gum.According to another variant, it consists essentially of said gum and atleast one plasticizer (at least one additive being present in smallamount), or even it consists of said gum and at least one plasticizer.

Said gum:

-   -   is chosen from polyurethane-polyester gums (i.e. of polyurethane        nature with flexible segments of polyester type),        polyurethane-polyether gums (i.e. of polyurethane nature with        flexible segments of polyether type) and mixtures thereof,    -   it has a number-average molecular weight of greater than 20 000        g/mol (advantageously greater than 50 000 g/mol, very        advantageously greater than 75 000 g/mol (very particularly with        reference to the ageing resistance of the final product), and    -   it has a Mooney viscosity of between 20 and 70 ML (5+4) at        100° C. This parameter is widely used in the rubber industry. “x        ML (5+4) at 100° C.” is understood as “x M=the viscosity in        Mooney units (or points); L or S (in this instance L)        corresponding to the size of the rotor, 5 indicating the        preheating time of the product and 4 is the time in minutes        after starting the motor at which the reading is taken, 100° C.        being the measuring temperature”. The value “x” is generally        given as “±y”; it is that value “x” which, according to the        invention, must be within the range 20-70 (limit values        included).

Such a gum is perfectly suitable for the purposes of the invention,insofar as, in the proportions indicated (from 10 to 22% only,remembering that products with a high charge rate are underconsideration), 1) it allows the (charges+gum) mixture to bemechanically worked at low temperature, i.e. at a temperature below 120°C., or even below 100° C. (which is entirely compatible with thestability of the charges present), and does so without the use ofsolvent; and 2) it gives the final product the required mechanical holdand cohesion.

The inventors have, to their credit, identified (selected) this type ofgum, which is perfectly suitable for the purposes of the invention.Other types of gum were tested and do not give satisfactory results (asregards the possibility of working the mixture at low temperature and/oras regards the properties of the final product).

A person skilled in the art has already understood that, with referenceto the first of the two stipulations of the requirement recalled above,the result may be further improved by incorporating at least oneplasticizer.

Said gum generally consists of a polyurethane-polyester or apolyurethane-polyether gum, but mixtures of at least two gums (at leasttwo polyurethane-polyester gums, at least two polyurethane-polyethergums or at least one polyurethane-polyester gum and at least onepolyurethane-polyether gum; such mixtures of gums (gums within themeaning of the invention) constituting a gum within the meaning of theinvention) having the required properties (recalled above) may be used.Said gum advantageously consists of a polyurethane-polyester gum.

The composition of the composite pyrotechnic products of the inventionis thus liable to contain at least one plasticizer. Such an at least one(energetic or non-energetic) plasticizer is generally present in aproportion of from 2% to 8% by weight (of the total composition). Suchan at least one plasticizer advantageously consists, with reference tothe force of the product, of at least one energetic plasticizer.

The composition of the composite pyrotechnic products of the inventionthus advantageously contains at least one energetic plasticizer (oneenergetic plasticizer, at least two energetic plasticizers, or at leastone energetic plasticizer and at least one non-energetic plasticizer),and very advantageously contains one energetic plasticizer.

The energetic plasticizer(s) under consideration are advantageously ofnitrate and/or nitramine type.

The energetic plasticizer(s) under consideration are very advantageouslychosen from diethylene glycol dinitrate (DEGDN), triethylene glycoldinitrate (TEGDN), butanetriol trinitrate (1317N), trimethylolethanetrinitrate (TMETN), a mixture of 2,4-dinitro-2,4-diazapentane,2,4-dinitro-2,4-diazahexane and 3,5-dinitro-3,5-diazaheptane (and mostparticularly DNDA 5,7), nitratoethylnitramines (especiallymethyl-2-nitratoethyl nitramine (methylNENA) and ethyl-2-nitratoethylnitramine (ethylNENA)), and mixtures thereof.

The composition of the composite pyrotechnic products of the inventionis thus constituted essentially, even constituted, of the energeticcharges and of the binder, based on said gum (binder=said gum orbinder=said gum+at least one plasticizer). It may be constituted to 100%by weight of said energetic charges and of said binder. It is generallythus constituted to at least 95% by weight, more generally to at least98% by weight. In effect, it cannot be excluded for it to contain inaddition at least one additive. Such an at least one additive, when itis present, is generally present in a proportion of from 0.1% to 2% byweight. It may especially be at least one formulation agent (candelillawax and/or paraffin wax, for example), and/or at least one stabilizer.

The composite pyrotechnic products of the invention, as described above,are entirely suitable as propellant powders for barrel weapons. Saidcomposite pyrotechnic products of the invention thus consistadvantageously of such powders. The composite pyrotechnic products ofthe invention, as described above, are also suitable, especially, astactical propergol, explosive composition and gas generator.

The major advantage of the products of the invention becomes apparentfrom the foregoing text. The products are advantageous per se (in termsof force, vulnerability and wide field of application with reference tothe nature of the charges) and insofar as they may be obtained via aprocess that is simple to perform (much easier to perform than theprocesses of the prior art).

Said process constitutes the second subject of the present invention. Itcomprises:

-   -   a) the provision of the ingredients below:        organic energetic charges,        a polymeric gum, chosen from polyurethane-polyester gums,        polyurethane-polyether gums and mixtures thereof, the        number-average molecular weight of which is greater than 20 000        g/mol and the Mooney viscosity of which is between 20 and 70 ML        (5+4) at 100° C.;    -   b) the mixture of these in suitable proportions relative to the        desired composition of the final product, to produce a pasty        mixture;    -   c) the production, from said pasty mixture, of the composite        pyrotechnic product(s) in the desired form.

It thus comprises the provision of the essential constituent ingredientsof the desired composite pyrotechnic products: the charges+the gum. Inaddition to said essential ingredients, it has been seen that at leastone plasticizer and at least one additive (especially such as aformulation agent and/or stabilizer) may be used.

With reference to each of the ingredients used for performing theprocess, reference may be made to the first part of the text relating tothe product.

In a first stage, using the ingredients identified above(charges+gum+optionally, at least one plasticizer+optionally, at leastone additive), a pasty mixture is thus prepared, which is the precursorof the targeted final product. Such a pasty mixture is advantageouslyprepared with a twin-screw extruder (by extrusion) or with a two-rollmill, depending on the amounts to be used. It is generally prepared at atemperature of between 60° C. and 120° C. (inclusive of extreme values).It is often prepared at a temperature of 80° C. It is understood thatthis mixing temperature depends on the type of gum and the presence orabsence of at least one plasticizer.

Starting with said pasty mixture, in the third step of the process ofthe invention, the product in the desired form is prepared (n productsare thus generally prepared). Said third step is thus analyzed as a stepof forming the paste. This forming may especially comprise spinning orcalendering. After such spinning (performed in a press cylinder, havingan outlet orifice of more or less substantial diameter), the spunproduct is generally chopped into strands (of the desired length). Suchstrands, which are suitable as propellant powders for barrel weapons,generally have a length of from 2 to 20 mm, for a diameter of from 1 to20 mm (more generally for a diameter of from 2 to 15 mm). On conclusionof such calendering, the calendered product, in the form of a plate(such a plate generally has a thickness of from 10 to 20 mm), isgenerally chopped into platelets.

According to implementation variants of the process of the invention,steps b and c of said process may comprise:

-   -   blending with a twin-screw extruder (or extrusion) and spinning,    -   blending with a two-roll mill and spinning, or    -   blending (with a twin-screw extruder or a two-roll mill) and        calendering.

It is now proposed to illustrate the invention, in a manner that is notin any way limiting, in its product and process aspects, via theexamples below.

1) Starting materials used

-   -   a) Commercial products        Gums: Millathane®76, sold by the company TSE Industries (product        of polyaddition of a urethane and a polyester). It has the        characteristics below:        Number-average molecular weight: 40 000 g/mol        Mooney viscosity: 35 (±10) ML (1+4) at 100° C.;    -   UREPAN® 641 G: sold by the company RheinChemie (product of        polyaddition of diphenylmethane diisocyanate and of a        polyester). It has the characteristics below:        Number-average molecular weight: 80 000 g/mol        Mooney viscosity: 45 (±10) ML (5+4) at 100° C.;    -   UREPAN® 643 G: sold by the company RheinChemie (product of        polyaddition of diphenylmethane diisocyanate and of a        polyester). It has the characteristics below:        Number-average molecular weight: 80 000 g/mol        Mooney viscosity: 40 (±10) ML (5+4) at 100° C.    -   a) Prepared products

Charges: EDNA

The synthesis of ethylene dinitramine (EDNA) was performed in two stagesvia the isolation of an intermediate: dinitroethyleneurea (DNEU), in wetform, which was then transformed into EDNA.

Concentrated nitric acid was introduced into a jacketed 50 cm³ reactor.The nitrating bath was then cooled to a reaction temperature at 0° C.Once the bath reached at 0° C., the introduction of imidazolidone wascommenced. This reagent was introduced slowly so as not to exceed 20° C.The DNEU precipitated as soon as its concentration in the medium wasgreater than 23% by weight. The introduction of imidazolidone into theheterogeneous medium (nitrating bath+solid DNEU) was continued.

After the end of introduction of the imidazolidone, the medium was leftstirring for 30 minutes at room temperature.

At the end of reaction, the mixture was poured into a bath of cold waterat about 5° C. with stirring. The solid was then separated from themother liquors by filtration, and washed several times with distilledwater to neutral pH, then drained by suction. It was then taken up, inwet form, for the synthesis of EDNA.

The decarboxylation step was performed by addition of DNEU to a hotaqueous solution buffered with sodium acetate. Evolution of gas (of CO₂)was observed, which necessitates portionwise introduction of the powder.

Once the introduction of the DNEU was complete, the mixture wasmaintained at a stage of 95° C. to complete the formation of EDNA.

The reaction medium was then cooled to make the EDNA precipitate. Thesuspension was then filtered and then dried. A yield of 85% wasobtained.

The production of EDNA was confirmed by infrared.

IR: 2936 cm⁻¹ aliphatic CH, 1593 cm⁻¹ NO₂, 1448 cm⁻¹ N=N, 1360 cm⁻¹ C-H.The EDNA crystals obtained are coarse crystals (they have a D₅₀ ofgreater than or equal to 100 μm (D₅₀=diameter for which the cumulativevolume percentage is 50%)). To use them, they are ground in a SWECO®mill. On conclusion of said grinding, they have a D₅₀ of 30 μm.

Plasticizer: TEGDN

Trioxyethylene glycol dinitrate (TEGDN) was obtained by nitration insulfonitric medium of trioxyethylene glycol.

2) Process for preparing composite pyrotechnic products of the invention

Composite pyrotechnic products of the invention of three types (Examples1, 2 and 3) were prepared and tested. Their weight composition and theirforce (measured or calculated) are given, respectively, in Tables 1, 2and 3 below. Below each of said Tables 1, 2 and 3, other characteristicsof said products are indicated.

These composite pyrotechnic products of the invention were obtained fromthe starting materials identified above.

Step b of the process of the invention: the pasty mixtures were obtainedin a two-roll mill, in a manner known per se. The gum was firstintroduced between the rollers of the two-roll mill (rolling mill),brought to a temperature of 65° C. It was thus softened. Next, acharges+plasticizer mixture (prepared beforehand in a container) wasadded. Candelilla wax was then subsequently added to the resultingmixture.

Step c of the process of the invention: the pasty mixtures obtained wereintroduced into a press cylinder heated to 80° C. to perform spinning ata pressure of between 280 and 320 bar. After chopping, powder strandswere obtained (diameter: 10 mm, length: 11 mm).

Example 1

TABLE 1 weight % Binder Millathane ® 76 14.6 20 TRENO 4.9 Candelilla wax0.5 Charge EDNA 80.0 80 100 F 0.985 measured (MJ/kg)

Characteristics of the product obtained (after mixing with the two-rollmill and spinning) are indicated below.

Mechanical properties at 20° C. in compression (10 mm/min):

-   -   Sm=0.9 MPa (maximum stress at break)    -   E=10.2 MPa (elastic modulus)    -   Em=14.2% (maximum crush before break).

Example 2

TABLE 2 weight % Binder UREPAN ® 641 G 14.6 20 TRENO 4.9 Candelilla wax0.5 Charge EDNA 80.0 80 100 F calculated (MJ/kg) 1.003

Characteristics of the product obtained (after mixing with the two-rollmill and spinning) are indicated below.

Mechanical properties at 20° C. in compression (10 mm/min):

-   -   Sm=13.7 MPa (maximum stress at break)    -   E=14.6 MPa (elastic modulus)    -   Em=1.4% (maximum crush before break)

Example 3

TABLE 3 weight % Binder UREPAN ® 643 G 15.1 18 TRENO 2.6 Candelilla wax0.3 Charge EDNA 82.0 82 100 F calculated (MJ/kg) 1.008

Characteristics of the product obtained (after mixing with the two-rollmill and spinning) are indicated below.

Mechanical properties at 20° C. in compression (10 mm/min):

-   -   Sm=7.9 MPa (maximum stress at break)    -   E=40.6 MPa (elastic modulus)    -   Em=29.7% (maximum crush before break).

1. A composite pyrotechnic product whose composition, expressed asweight percentages, contains: from 78% to 90% of organic energeticcharges, and from 10% to 22% of a polymeric gum, chosen frompolyurethane-polyester gums, polyurethane-polyether gums and mixturesthereof, a number-average molecular weight of which is greater than 20000 g/mol and a Mooney viscosity of which is between 20 and 70 ML (5+4)at 100° C.
 2. The composite pyrotechnic product as claimed in claim 1,wherein said organic energetic charges consist of hexogen, octogen,nitroguanidine, ethylene dinitramine, N-guanylurea dinitramide,1,1-diamino-2,2-dinitroethylene, bis(triaminoguanidinium)5,5′-azotetrazolate, dihydrazinium 5,5′-azotetrazolate,5,5′-bis(tetrazolyl)hydrazine, bis(2,2-dinitropropyl)nitramine, anitropyrazole, or a mixture of such charges.
 3. The compositepyrotechnic product as claimed in claim 1, wherein said organicenergetic charges contain ethylene dinitramine charges.
 4. The compositepyrotechnic product as claimed in claim 1, wherein said polymeric gumhas a number-average molecular weight of greater than 50 000 g/mol. 5.The composite pyrotechnic product as claimed in claim 1, wherein saidgum is a polyurethane-polyester gum or a polyurethane-polyether gum. 6.The composite pyrotechnic product as claimed in claim 1, wherein thecomposition also contains at least one energetic or non-energeticplasticizer; said plasticizer representing from 2% to 8% by weight ofthe composition of said pyrotechnic product.
 7. The compositepyrotechnic product as claimed in claim 6, wherein said at least oneplasticizer is an energetic plasticizer of nitrate and/or nitraminetype.
 8. The composite pyrotechnic product as claimed in claim 7,wherein said at least one plasticizer is chosen from diethylene glycoldinitrate, triethylene glycol dinitrate, butanetriol trinitrate,trimethylolethane trinitrate, a mixture of 2,4-dinitro-2,4-diazapentane,2,4-dinitro-2,4-diazahexane and 3,5-dinitro-3,5-diazaheptane,nitratoethylnitramines, and mixtures thereof.
 9. The compositepyrotechnic product as claimed in claim 1, wherein the composition alsocontains from 0.1% to 2% by weight of at least one additive.
 10. Thecomposite pyrotechnic product as claimed in claim 1, wherein thecomposite pyrotechnic product consists of a propellant powder for barrelweapons.
 11. A process for preparing at least one composite pyrotechnicproduct as claimed in claim 1, the process comprising: a) providing theingredients below: organic energetic charges, a polymeric gum, chosenfrom polyurethane-polyester gums, polyurethane-polyether gums andmixtures thereof, a number-average molecular weight of which is greaterthan 20 000 g/mol and a Mooney viscosity of which is between 20 and 70ML (5+4) at 100° C.; b) mixing the ingredients in suitable proportionsrelative to the desired composition of the final product, to produce apasty mixture; and c) producing, from said pasty mixture, said at leastone composite pyrotechnic product in a desired form.
 12. The process asclaimed in claim 11, further comprising providing at least one energeticor non-energetic plasticizer and/or at least one additive, and mixing ofsaid charges and gum with said at least one plasticizer and/or said atleast one additive to obtain a pasty mixture.
 13. The process as claimedin claim 11, wherein said mixture is prepared with a twin-screw extruderor a two-roll mill.
 14. The process as claimed in claim 11, wherein saidmixture is prepared at a temperature of between 60° C. and 120° C. 15.The process as claimed in claim 11, wherein said at least one compositepyrotechnic product is obtained by spinning or calendering.
 16. Thecomposite pyrotechnic product as claimed in claim 1, wherein thecomposition, expressed as weight percentages, contains from 80% to 86%of organic energetic charges.
 17. The composite pyrotechnic product asclaimed in claim 3, wherein said organic energetic charges containhexogen charges and ethylene dinitramine charges.
 18. The compositepyrotechnic product as claimed in claim 4, wherein said polymeric gumhas a number-average molecular weight of greater than 75 000 g/mol. 19.The composite pyrotechnic product as claimed in claim 5, wherein saidgum is a polyurethane-polyester gum.
 20. The composite pyrotechnicproduct as claimed in claim 6, wherein the composition further containsan energetic plasticizer.